Latching mechanism with temperature-responsive blocking device



April 15,1959 K H. ERICKSON 3,438,666

LATCHING MECHANIM WITH TEMPERATURE-RESPONSIVE BLOGKING DEVICE Filed Mayl0. 1967 sheetv @f2 jlwfommsx/ Aprll 15, 1969 K. H. ERICKSON 3,438,656

LATCHING MECHANISM WITH TEMPERATURE-RESPONSIVE BLOCKING DEVICE :filedMay lo, 1967 v sheet 2 of 2 United States Patent 3,438,666 LATCHINGMECHANISM WITH TEMPERATURE- RESPONSIVE BIACKING DEVIQE Karl H. Erickson,Rockford, Ill., assigner to Amerock Corporation, Rockford, Ill., acorporation of Connecticut Filed May 1t), 1967, Ser. No. 637,504 Int.Cl. Etl'b 5]/00, 65/44 U.S. Cl. 292-210 8 Claims ABSTRACT oF THE"piscLosURE A temperature-responsive blocking device having a blockingmember which is rotated into blocking relation with a latch for aself-cleaning oven to prevent movement of the latch to an unlatchedposition when the temperature of the oven is above a predeterminedvalue. The blocking member is rotated solely by the action of a spiraledbimetallic coil which is subjected only to thermal stresses imposed bynormal expansion and contraction of the met'al strips forming the coil.

Background of the invention` Summary of the invention The primary aim ofthe present invention is to provide a new and improved blocking deviceof the above character which remains more precisely sensitive totemperature changes throughout its service life than prior arrangementsof the same general type and which, at the same time, may be calibratedmore easily and accurately to cause the blocking member to rotate intoits blocking position at a precisely selected temperature. In a moredetailed aspect, the invention contemplates a novel blocking device inwhich the position of the blocking member is determined exclusively bythe natural thermally stressed condition of the bimetallic coil, and inwhich the coil is substantially free of external mechanical forces inall positions of the blocking member thereby to reduce the likelihood ofover-stressing the coil.

To achieve these ends, the blocking member is rotated into and out ofblocking relation with the latch solely by the action of the coil as thelatter winds and unwinds in response to temperature changes. Moreover,the blocking member is left free to rotate to any position demanded bythe thermally stressed coil without restricting normal expansion andcontraction of the coil. Since no external mechanical force is used torotate the blocking member and since the coil is free to expand andcontact in accordance with its natural tendencies, the danger ofoverstressing the coil and destroying its sensitivity is substantiallyeliminated.

Brie]t description of the drawings FIGURE 1 is a fragmentary verticalcross-section of an exemplary applicance equipped with a latchingmechanism having a blocking device embodying the novel features of thepresent invention.

FIG. 2 is a fragmentary cross-section taken substantially along the line2-2 of FIG. 1 and showing the 3,438,666 Patented Apr. 15, 1969 ICC partswith the latch in a latched position and with the blocking member in aninactive position.

FIG. 3 is a fragmentary cross-section taken substantially along the line3 3 of FIG. 1.

FIG. 4 is a fragmentary cross-section. taken substantially along theline 4 4 of FIG. 3.

FIG. 5 is a fragmentary view similar to FIG. 2 but showing the blockingmember in an active position.

FIG. `6 is a fragmentary view similar to FIG. 5 but showing the blockingmember in an intermediate position.

FIG. 7 is an enlarged exploded perspective view of part of the blockingdevice.

Detailed description As shown in the drawings for purposes ofillustration, the invention is embodied in a latching mechanismcornprising a latch 10 mounted within the cabinet 11 of an appliancesuch as a self-cleaning oven and having an elongated bolt 13 selectivelyengageable with a strike 14 on the oven door 15 to latch the door in atightly closed position prior to operation of a high-temperaturecleaning unit (not shown) for burning olf food and grease from the ovenwalls. In such a latch, an operating lever 16 is pivoted on a supportingbase 17 is connected to the bolt in such a manner that counterclockwiseswinging of the lever from an unlatched position shown in phantom inFIG. 2 to a latched position shown in full results in correspondingmovement of the bolt from an unlatched position to a latched position inwhich a hooked outer end 19 of the bolt is disposed in engagement withthe strike to hold the door tightly sealed against the cabinet. Toprevent activation of the high-temperature cleaning unit when the dooris open or free to open, a safety switch 20 is connected electricallyinto the control circuit of the unit and is positioned on the base 17 tobe closed by the lever as the latter moves to its latched position sothat the circuit will be conditioned for operation only when the door isclosed and latched.

Only a brief description of the latch 10 itself will be presented hereinsince reference may be had to my copending application Ser. No. 622,142,led Mar. l0, 1967, for more specific details of the construction andoperation of a latch of this type. In general, the supporting base 17 isdisposed between the oven and the top wall 21 of the cabinet 11 and ismounted on an upper oven wall 23 which is separated from the oven liner24 by a layer of insulation 25. The operating lever 16 is generally U-shaped in elevation and comprises upper and lower horizontal plates 26and 27, the lower plate being connected pivotally to the base by a rivet29 and being joined to the upper plate by an upright wall 30 (FIG. 3)extending between the two plates. To swing the lever about the axis ofthe rivet between its unlatched and latched positions, a handle 31accessible from the front of the cabinet is fastened at its inner end tothe upper plate 26 and projects outwardly through a slot 33 locatedbetween the top of the door 15 and the top wall 21 of the cabinet. Asthe handle is moved manually back and forth in an arc along the front ofthe cabinet, the corresponding motion of the lever is transmitted to thebolt 13 by a driving link 34 whose outer end is pivotally connected tothe bolt by a rivet 35 and whose inner end is similarly connected to thelower lever plate 27 by a rivet 36. The bolt is mounted for compoundpivoting and sliding movement on the rivet 29 and is moved into and outof engagement with the strike 14 (see FIG. 2) as the lever is swung backand forth between the unlatched and latched positions.

I-n appliances operated under high temperature conditions, it isdesirable to prevent unlatching and opening of the door when theoperating temperature is above a dangerous level. For example, openingof the door 15 of a self-cleaning oven during operation of thehigh-temperature cleaning unit would allow smoke and odors to escapefrom the oven chamber and would admit oxygen into the chamber thuscreating the danger of a sudden llame. In the present instance, movementof the latch 10 to the unlatched position when the temperature withinthe oven exceeds a predetermined safe value is prevented by a blockingdevice 37 including a blocking member 39 which is rotated into blockingrelation with the latch (see FIG. in response to the expansion of aspiraled bimetallic coil 40 adapted to Sense the temperature within theoven.

The present invention contemplates a novel blocking device 37 in whichthe blocking member 39 is rotated into and out of blocking relation withthe latch solely by the action of the bimetallic coil 40, is alwayspositioned exactly in accordance with the natural thermally stressedcondition of the coil, and is left free to rotate to any positiondemanded by the coil without restricting normal expansion andcontraction of the coil. For these purposes, the Winding and unwindingaction undertaken by the coil in response to changes in temperature isused to full advantage to rotate the blocking member into and out ofblocking relation with the latch without the air of external mechanicalforces. In the blocking position, the blocking member preventsunlatching of the latch and yet is free to move relative to the latch soas to permit the coil to expand in accordance with its naturaltendencies. As a result, the danger of mechanically overloading the coiland destroying its sensitivity is eliminated since the coil is alwaysfree of stresses imposed by mechanical rforces.

In the present instance, the blocking member 39 is centrally located onthe upper side of the inner end portion of the base 17 and is fastenedto the upper end of a vertical shaft 41 (FIG. 3) rotatably m-ounted inthe base and projecting downwardly through the upper oven wall 23 to thelevel of the oven liner 24. Near its lower end, the shaft is journaledin a horizontal portion 43 of an angularly bent bracket 44 fastened tothe underside of the base by rivets 45. The bimetallic coil 40 isconnected to the lower end of the shaft and, as the coil winds andunwinds in response to temperature changes in the oven, the shaft isrotated about its own axis thereby turning the blocking member back andforth between an active position (FIG. 5) blocking unlatching of thelatch 10 and an inactive position (FIG. 1) leaving the latch free formovement to the unlatched position. To prevent the insulation 25 fromrestricting rotation of the shaft, a semicylindrical shield 46 (FIG. 3)extends along the shaft and is fastened to a vertical portion 47 of thebracket 44, the shield and the bracket thus coacting to form anenclosure surrounding the shaft.

As shown most clearly in FIGS. 3 and 4, the coil 40 comprises a pair ofdissimilar resilient metal strips such as brass and iron bonded togetherin face-to-face relation and wound spirally about the axis of the shaft41. An inner end 49 of the coil is bent inwardly from the inner turn ofthe coil and is clamped rigidly within a vertical slot 50 formed in thelower end of the shaft. To anchor the coil relative to the shaft, anouter end 51 of the coil is bent outwardly and projects loosely througha slot 53 formed in a vertical lower leg 54 integral With and dependingfrom the horizontal portion 43 of the bracket 44. The coil is protectedfrom the insulation 25 by a shroud 55 (FIGS. 1 and 3) fastened to thebracket 44 and enclosing all of the coil except the lower side thereofwhich is exposed directly to the heat in the oven chamber. Since thecoil herein unwinds as the metal strips expand, the shaft and theblocking member 39 are turned counterclockwise by the inner end 49 ofthe coil as the temperature increases in the oven chamber, In allpositions of the blocking member, the metal strips are subjected only tostresses imposed by thermal expansion and contraction and are neverwound mechanically against their own resiliency. Thus, when consideredas a spring, the coil is always relaxed and the inner end 49 thereofexerts substantially no lforce on the edges of the anchoring slot 53 inthe bracket 44. That the coil is never wound spring fashion isillustrated by the fact that the relative positioning of the ends 49 and51 at a given temperature before installation of the coil is exactly thesame as the relative positioning of the ends at the same temperatureafter the coil has been installed and has been in normal service use.

Preferably, the blocking member 39 is formed by a lug 57 (FIG. 7)integral with an upstanding from one end of a flat plate 59 adapted tobe coupled for rotation in yunison with the shaft 41 and disposed belowthe level of the lower lever plate 27. When the oven is at roomtemperature, the blocking member is disposed in the inactive position(FIG. 5) in which the lug is spaced angularly from an inner extension 60of the lower lever plate 27 and is positioned out of the path followedby the extension during counterclockwise movement of the operating lever16 from the latched position to the unlatched position. With theblocking member in the inactive position, the extension simply passes bythe lug and over the plate 59 to permit free movement of the leverbetween its positions.

As the temperature within the oven begins to increase, the bimetalliccoil 40 expands and unwinds so that the inner end 49 of the coil beginsto rotate the shaft 41 to move the lug 57 counterclockwise in an arcuatepath, the position of the lug in the path being determined exclusivelyby the natural thermally stressed condition of the coil. When theself-cleaning unit is being used and initially raises the temperature ofthe oven to a preselected value such as 600 F., the lug is turned to anintermediate position (FIG. 6) in which the leading edge of a curvedouter abutment surface 63 of the lug is disposed just within the pathfollowed by a relatively long arcuate abutment surface 64 of slightlygreater curvature formed on the lever extension 60 and spaced about l/16of an inch from the lug. Accordingly, the lug Will engage the extensionupon initial movement of the operating lever 16 toward the unlatchedposition and will block complete unlatching movement of the leverthereby to prevent opening of the door 15 when the cleaning unit isoperatmg.

Continued operation of the cleaning units increases the temperature ofthe oven to a maximum level of about 900 F. The lug 57 thus continues toturn counterclockwise in the active portion of the arcuate path andmoves to the final position (FIG. 6) in which the abutment surface `63is face-to-face with the abutment surface 64 to block unlatching of thelatch. During such turning, the lug moves freely past the extension `60since the abutment surfaces 63 and 64 are spaced `from each other andsince the active portion of the arcuate path is sutlciently long topermit rotation of the lug to any position demanded by the coil 40 asthe temperature in the oven is raised to a maximum value. As a result,the latch does not engage and restrict rotation 'of the blocking member39 to interfere with normal expansion of the coil 40. The latter thus isnever in danger of being mechanically overstresed and therefore willremain precisely sensitive to temperature changes throughout the servicelife of the oven.

To enable calibration of the blocking device 37, that is, to set the lug57 for rotation into the intermediate position (FIG. 6) at precisely 600F. the blocking member 39 is adapted to be adjusted angularly about theaxis of the shaft 41. For this purpose, the upper end portion 65 (FIG.7) of the shaft project loosely through a hole 66 formed in the mountingplate 59 of the blocking member to leave the latter free for rotation onthe shaft. The mounting plate rests on a fiat base plate 67 rigid withthe upper end of the shaft and is coupled for rotation with the baseplate and the shaft by a screw 69 projecting through an arcuate slot 70formed in the mounting plate and threaded into a hole 71 in the baseplate. To calibrate the blocking device, the screw 69` is loosened andthe temperature is raised to 600 F. The blocking member 39 then isrotated about the shaft to adjust the lug 57 to the position shown inFIG. 6 thereby positioning the lug in accordance with the thermallystressed condition of the coil 40 at that temperature. Thereafter, thescrew is tightened to hold the blocking member in its selected angularposition on the shaft and the base plate 67. This calibration isrelatively simple since the workman easily can see when the lug V57 ispositioned properly with respect to the extension `60. Moreover, onlythe characteristics of the coil need be taken into account in making theadjustment since the coil is the only instrumentality affecting theposition of the lug.

I claim as my invention:

1. In a latching mechanism adapted to be held in a latched conditionunder certain operating temperatures, the combination of, a support,alatch mounted on said support for movement between latched and unlatchedpositions, a first abutment surface on said latch and movable along apredetermined path as the latch is moved from said latched position tosaid unlatched position, a blocking member mounted for rotation on saidsupport and having a second abutment surface movable in an arcuate path,first along an inactive portion disposed out of said first path and thenalong an active portion disposed in said first path but spaced from saidfirst abutment surface, the length of said active portion beingproportional to a range of temperatures varying from a predeterminedvalue to a normal maximum operating value, said second abutment surfacebeing operable when positioned in said active portion of said arcuatepath to engage said first abutment surface after initial movement of thelatch toward said unlatched position thereby to block complete movementof the latch toward said unlatched position, a bimetallic coil havingone end fastened to said support and having an opposite end fastened tosaid blocking member and movable relative to said one end as said coilwinds and unwinds in response to temperature changes thereby to rotatesaid second abutment surface to a position in said arcuate pathprecisely correlated with the natural thermally stressed condition ofthe coil at any given temperature, said coil holding said secondabutment surface in said inactive portion of said arcuate path when thetemperature is below said predetermined value and being thermallyexpanded to turn said second abutment surface into said active portionwhen the temperature exceeds said predetermined value, and said secondabutment surface moving freely alongside said first abutment surfaceduring such turning by virtue of the spacing between the two surfacesand moving to any position demanded by said coil without restrictingnormal expansion thereof by virtue of the length of said active portionof said arcuate path.

2. A latching mechanism as defined in claim 1 in which said firstabutment surface is arcuately curved on a greater radius that thearcuate path and is at least equal in length to the active portion ofsaid path.

3. A latching mechanism as defined in claim 1 further including a shaftjournaled in said support and mounting said blocking member for rotationon the support, said opposite end of said coil being fastened to saidshaft to rotate the latter, and adjustable means normally coupling saidshaft and said blocking member for rotation in unison, said means beingselectively releasable from said blocking member to leave the blockingmember free for rotation about said shaft and thereby permit adjustmentof the angular position of said second abutment surface in said arcuatepath independently of said coil.

4. In a latching mechanism adapted to be held in a latched conditionunder certain operating temperatures, the combination of, a support, alatch mounted on said support for movement between latched and unlatchedpositions, a first abutment surface on said latch and movable along afirst path as the latch is moved from said latched position to saidunlatched position, a blocking member mounted for movement on saidsupport and having a second abutment surface movable in a second path,first along an inactive portion disposed out of `said first path andthen along an active portion disposed in said first path, the length ofsaid active portion being proportional to 4a range of temperaturesvarying from a predetermined value to a normalmaximum operating value,said second surface being spaced from said first surface when positionedin said active portion and being operable to engage said first surfaceafter initial movement of the latch toward said unlatched positionthereby to block complete movement of the latch to the unlatchedposition, a spiraled bimetallic coil having one end fastened to saidsupport and having an opposite end operably connected to said blockingmember and movable relative to said one end as the coil winds andunwinds in response to temperature changes thereby to move said secondsurface to a position in said second path precisely correlated with thenatural thermally stressed condition of the coil at any giventemperature, said coil holding said second surface within said inactiveportion of said second path when the temperature is below saidpredetermined value and unwinding to shift said second abutment surfaceinto the active portion of said second path when the temperature exceedssaid predetermined value, and said second surface moving freely alongthe active portion during such shifting by virtue of the spacing betweenthe two surfaces and of the length of the active portion.

5. In a latching mechanism adapted to be held in a latched conditionunder certain'operating temperatures, the combination of, a support, alatch mounted on said support for movement between latched and unlatchedpositions, a first abutment surface on said latch and movable along afirst path as the latch is` moved from said latched position to saidunlatched position, a blocking member mounted for rotation on saidsupport and having a second abutment surface movable in an arcuate path,first along an active portion disposed out of said first path and thenalong an inactive portion disposed in said rst path, the length of saidactive portion being proportional to a range of temperatures varyingfrom a predetermined value to a normal maximum operating value, saidsecond surface being spaced from said first surface when positioned insaid active portion of said arcuate path and being operable to engagesaid first surface after initial movement of said latch toward saidunlatched position thereby to block complete movement of the latch tothe unlatched position, a bimetallic element connected between saidblocking member and said support and operable to expand and contract inresponse to temperature changes thereby to rotate said second surface toa position in said arcuate path precisely correlated with the naturalthermally stressed condition of the element at any given temperature,said element holding said second surface within said inactive portion ofsaid arcuate path when the temperature is below said predetermined valueand being stressed thermally to turn said second surface into saidactive portion when the temperature exceeds said predetermined value,and said second surface moving freely relative to said ii-rst surfaceand moving freely along the active portion during such turning by virtueof the spacing between the two surfaces and by virtue of the length ofthe active portion.

6. In a latching mechanism adapted to be held in a latched conditionunder certain temperature environments, the combination of, a support, alatch mounted on said support and movable along a predetermined pathfrom a latched position to an unlatched position, a blocking membermounted on said support for rotation in an arcuate path between aninactive position disposed out of said first path and an active positiondisposed in said rst path and engageable with said latch to blockmovement of the latter from said latched position to said unlatchedposition, a spiraled bimetallic coil having a one end held on saidsupport and having an opposite end connected to said blocking member andmovable relative to said one end as the coil Winds and unwinds inresponse to temperature changes thereby to turn the blocking member to aposition in said arcuate path `determined exclusively by the naturalthermally stressed condition of the coil at any given temperature, saidcoil holding said blocking member in said inactive position at normalroom temperature and being stressed thermally to positively rotate theblocking member to said active position when the temperature increasesto a value signicantly higher than room temperature, and said coil beingmechanically unstressed at normal room temperature with said one endexerting substantially no force on said support.

7. A latching mechanism as dened in claim 6 in which the relativepositioning of the ends of the coil at normal room temperature beforeinstallation of the coil and before fastening of the ends to theblocking member and the support is exactly the same as the relativepositioning of the ends at normal room temperature after installation ofthe coil and after the coil has rotated said blocking member back andforth between said active and inactive positions in normal operatingfashion.

8. A latching mechanism as defined in claim 6 in which said blockingmember is rotatably mounted on a shaft journaled in said support, saidopposite end of said coil being fastened to said shaft to yrotate thelatter, and adjustable means normally coupling said shaft and saidblocking member for rotation in unison, said means being selectivelyreleasable from said blocking member to leave the blocking member freefor rotation about said shaft and thereby permit adjustment of theangular position of the blocking member independently of said coil.

References Cited UNITED STATES PATENTS 2,598,067 5/1952 OBrien 110-183,05 0,048 8/ 1962 Scott 126-273 3,362,398 1/1968 Fane 126-273 MARVIN A.CHAMPION, Primary Examiner.

JOHN R. MOSES, Assistant Examiner.

U.S. Cl. X.R.

